Fatty Acids as Phase Change Materials (PCMs) for Thermal Energy Storage: A Review

Abstract

Thermal energy storage (TES) technologies in general and phase change materials (PCMs) in particular, have been topic in research for the last 20 years. Traditionally, available heat has been stored in the form of sensible heat (typically by raising temperature of water, rocks, etc). Latent heat storage on the other hand, is a novel and developing technology, which has found considerable interest due to its operational advantages of smaller temperature swing, smaller size, and lower weight per unit of storage capacity. The interest on thermal energy storage by using fatty acids as PCM has risen in recent times since they have desired thermodynamic and kinetic criteria for low temperature latent heat storage. An added advantage is that fatty acids are derived from the vegetable and animals oil that provides an assurance of continuous supply. This article will review the development of fatty acids as PCMs for solar thermal energy storage application.     

Impact of anthropogenic heat emissions on meteorological parameters and air quality in Beijing using a high-resolution model simulation

• The Large scale Urban Consumption of energY model was updated and coupled with WRF. • Anthropogenic heat emissions altered the precipitation and its spatial distribution. • A reasonable AHE scheme could improve the performance of simulated PM_2.5. • AHE aggravated the O₃ pollution in urban areas. Anthropogenic heat emissions (AHE) play an important role in modulating the atmospheric thermodynamic and kinetic properties within the urban planetary boundary layer, particularly in densely populated megacities like Beijing. In this study, we estimate the AHE by using a Large-scale Urban Consumption of energY (LUCY) model and further couple LUCY with a high-resolution regional chemical transport model to evaluate the impact of AHE on atmospheric environment in Beijing. In areas with high AHE, the 2-m temperature (T₂) increased to varying degrees and showed distinct diurnal and seasonal variations with maxima in night and winter. The increase in 10-m wind speed (WS₁₀) and planetary boundary layer height (PBLH) exhibited slight diurnal variations but showed significant seasonal variations. Further, the systematic continuous precipitation increased by 2.1 mm due to the increase in PBLH and water vapor in upper air. In contrast, the precipitation in local thermal convective showers increased little because of the limited water vapor. Meanwhile, the PM_2.5 reduced in areas with high AHE because of the increase in WS₁₀ and PBLH and continued to reduce as the pollution levels increased. In contrast, in areas where prevailing wind direction was opposite to that of thermal circulation caused by AHE, the WS₁₀ reduced, leading to increased PM_2.5. The changes of PM_2.5 illustrated that a reasonable AHE scheme might be an effective means to improve the performance of PM_2.5 simulation. Besides, high AHE aggravated the O₃ pollution in urban areas due to the reduction in NO_x.     

冷循环便携式半导体降温服设计及制冷性能分析

为缓解高温环境下劳动人员面临的热害问题,设计1种利用半导体制冷片作为制冷源的便携式冷循环降温服,并在高温环境下测试其降温性能.结果表明:在总电源功率100 W、环境温度30℃的情况下,运行12 min后,制冷水温度降低至15.7℃.降温服稳定运行状态下制冷功率为340.4 W.系统运行环境温度对制冷系统的制冷性能有显著...     

余热锅炉在绿色油田建设中的应用

余热锅炉的运用使得不同品级的能源可以得到充分合理的利用。中国石油塔里木油田公司在生产实践中,采用燃气发电机组—余热锅炉联合循环技术,用不能再发电的燃气尾气生产蒸汽,对天然气中蕴含的能量进行分级利用,实现了发电、供热双重效益,也降低了对周边环境的热污染。文章对该热电联合循环的工艺流程进行介绍,通过对燃气发电机组尾气的能量传递进行计算,用热力学原理进行分析,以期实现对使用余热锅炉后的热电联产经济性进行综合评价的目的。     

A material and energy flow model for co-production of heat and power

Co-production of electricity, district heat and industrial heat/process steam (heat and power, CHP) has been applied to a large, national scale, in only a few countries in the world, Denmark, The Netherlands and Finland. In this production method, the waste energy from electricity production is used in two quality levels. First, industrial process steam requirements can be met with this residual energy. Second, the waste energy is used in local district heating networks for households and other buildings in a city. In this integrated production method, a total fuel efficiency of 85% can be achieved. Through the technique of fluidized bed combustion, modern CHP plants can use coal and oil, and in addition, heterogeneous fuels such as biomass, industrial wastes and recycled fuels from households. In this paper, the CHP method is considered in terms of four categories of material and energy flows. For the purpose of considering the potential environmental gains and the difficulties of this production method when applied to integrated waste management and energy production, the four suggested categories are: matter (biomass) (1), nutrients (2), energy (3) and carbon (4). Corporate environmental management inventory tools, decision-making tools, management, organisational and administrative tools as well as information management tools that could be used in CHP-related material and energy flow management are shortly discussed. It is argued that for CHP energy and environmental management, it can be important to adopt an approach to networks of firms, rather than to an individual firm. The presented material and energy flow model may contribute to assessing, planning and implementing of CHP-based waste management and cleaner energy production.     

操作条件对膜生物反应器运行经济性的影响

以运行费用作为膜生物反应器(MBR)运行经济性的考核指标,建立了MBR运行费用的计算模型,重点考察了膜通量、曝气强度、抽停时间、混合液悬浮固体质量浓度等操作条件对MBR运行经济性的影响.结果表明,膜通量在临界值5 L/(m2·h)时运行费用处于最低值;曝气强度过高或过低都会使系统运行费用增加,而经济曝气强度(气水比)为30:1;当抽吸时间≤12 min、停抽时间≥3 min时,运行费用变化缓慢,但抽吸时间或停抽时间超过临界值后,运行费用迅速上升;混合液悬浮固体质量浓度高于5.0 g/L时,运行费用随混合液悬浮固体质量浓度增加迅速递增.工程运行表明,运行费用模型预测值与实际值具有较好的一致性.     

Atmospheric mercury emissions from polluted gold mining areas (Venezuela)

Soil, waste rock and mud from mercury-gold amalgamation mining areas of El Callao (Venezuela) are highly enriched in Hg (0.5–500 μg g⁻¹) relative to natural background concentrations (<0.1 μg g⁻¹). Mercury fluxes to the atmosphere from twelve polluted sites of this area were measured in situ (6 a.m. to 8 p.m.) using a Plexiglas flux chamber connected to a portable mercury analyzer (model RA-915+; Lumex, St. Petersburg, Russia). Mercury fluxes ranged between 0.65 and 420.1 μg m⁻² h⁻¹, and the average flux range during the diurnal hours␣was 9.1–239.2 μg m⁻² h⁻¹. These flux values are five orders of magnitude higher than both reported world background Hg fluxes (1–69 ng m⁻² h⁻¹) and the regional values, which are in the range 2–10 ng m⁻² h⁻¹. The flux results obtained in this study are, however, similar to those measured at Hg polluted sites such as chloro-alkali plants or polymetallic ore mining districts (>100,000 ng m⁻² h⁻¹). The results from this study also show that Hg emissions from the soil are influenced by solar radiation, soil temperature and soil Hg concentration. Our data suggest that solar radiation may be the dominant factor affecting Hg° emission since the major species of mercury in polluted soil is Hg° (85–97% of total Hg). The simple release of Hg° vapor is probably the dominant process occurring with incident light in the field. The apparent activation energy for mercury emission indicates that the volatilization of mercury mainly occurred as a result of the vaporization of elemental mercury in soil. The degree of Hg emission differed significantly among the soil sites studied, which may be due to variations in soil texture, organic matter content and soil compaction.     

铜铝复合式CPU风冷散热器的实验研究

随着计算机的迅猛发展，CPU芯片的集成度、封装密度以及工作频率的不断提高，其发热量也不断增大，从而对CPU散热器的散热性能的要求也提高了．通过分析散热器的散热性能及性能评价方法，对放射状铜铝复合式CPU散热器进行了测试，建立不同风速下功率与CPU表面平衡温度关系曲线和不同风速下功率与热阻关系曲线，为改进散热器提供了实验数据．图3，参5．     

构筑根孔湿地中金属元素的来源、分布及其累积效应

石臼漾湿地是我国最大的饮用水源处理湿地,成为微污染水源水质改善的典范案例,已运行超过4年,主要运用人工湿地生态根孔技术、多级塘/植物床-沟壕系统协同净化技术来净化微污染水源.为了探明多级塘/植物床-沟壕系统对源水中常规金属K、Na、Ca、Mg、Al、Fe与重金属Cd、Cr、Cu、Ni、Zn、Pb的累积效应,研究了嘉兴石臼漾湿地岸边带与植物床-沟壕系统中沉积物/土壤的金属分布与累积量.结果表明,沉积物中的金属(Mg除外)均发生了富集和累积(富集系数EF∈(1.5,10.5)1.5).湿地内重金属潜在生态风险指数(RI∈(24.7,128.9)150)基本处于轻微风险水平,其最高值出现在湿地前端约1/8处的预处理塘(RI=174.94150).总体而言,重金属风险指数随水力流程而逐步降低.在湿地前端的预处理河道、预处理塘内,重金属沉积通量(23.97~157.72 mg·m-2·d-1)较高,而植物床-沟壕系统的沉积通量((38.80±16.17)mg·m-2·d-1)相对较低.占湿地面积11.35%的预处理河道、预处理塘中沉积的重金属高达9941.65 kg,占全湿地沉积量的37.90%,是重金属沉积的关键区域.而占湿地面积57.23%的植物床-沟壕系统中截留的重金属高达10601.89 kg,占全湿地沉积量的40.41%,是重金属去除的重点区域.湿地对重金属的主要持留机制是沉积作用,在湿地中单位平均沉积通量高达32.19 mg·m-2·d-1.据估算石臼漾湿地可沉积重金属6558.40 kg·a-1,植物吸收重金属约13.16 kg·a-1.本研究证明,多级塘/植物床-沟壕系统协同净化机制能够有效持留微污染水源中的金属特别是重金属,从而有效降低石臼漾湿地净化后源水的潜在生态风险.